NWS Forecast Discussion
096
FXUS61 KCTP 050320
AFDCTP
Area Forecast Discussion
National Weather Service State College PA
1020 PM EST Tue Feb 4 2025
.SYNOPSIS...
* Cooler and dry today with a brisk northwest wind gusting into
the mid and upper 20s (MPH). Wind decreases tonight with
increasing high clouds.
* Light snow on Wednesday across southern PA will precede the
arrival of a wintry mix of sleet and freezing rain Wednesday
night into Thursday with significant accumulation likely
across the Laurel Highlands.
* Another storm system could bring a wintry mix to Central
Pennsylvania this weekend.
&&
.NEAR TERM /UNTIL 7 AM WEDNESDAY MORNING/...
Shortwave trough passing N of LO is generating very light lake-
enhanced snow (just flurries) in nrn OH and far NWrn PA. Other
than a flurry or two across the N, we`ll remain dry for the
night.
Prev...
Varying amounts of stratocu with just a few flurries or brief
light SHSN will occur across the Northern Mtns through 23z
before dissipating as the DGZ that`s occupying the upper 2-3 kft
of the cloud layer dips a few KFT and the cloud layer thins out.
mid and high clouds will be on the increase from the west
tonight and by 07-09Z Wednesday, the entire region should be
mainly OVC with bases as low as 7-8 kft AGL across the SW third
of the state.
Mid afternoon temperatures display a healthy, 20-22 deg F range
from the NW Mtns to the Lower Susq Valley in the wake of last
night cfropa.
Low temperatures tonight will vary from the teens (north) to
upper 20s (south) which will equate to 5 to 10 deg F above
normal.
&&
.SHORT TERM /7 AM WEDNESDAY MORNING THROUGH THURSDAY/...
Aside from some virga or perhaps some light snow in a WNW to ESE
band across our Southern Counties and perhaps the Laurel
Highlands (fueled by mid to high level ascent within the
thermally direct cell/right entrance region of a strong 130-140
KT 250 mb jet stretched from KBUF to KLGA), the bulk of the
region will stay precipitation free for most of the day on
Wednesday.
Some of the blended models and latest CAMS members are still
displaying the potential for this rather narrow, quasi stnry
stripe of steady light to moderate fgen snow, but have backed
off somewhat from 24 hours ago.
By Wednesday evening, broad east to southeast near sfc flow in
the wake of retreating high pressure will keep cold air locked
in east of the Allegheny Mountains/Laurel highlands as a 6-9
hour period of rather strong low to mid level warm advection
from the south- southwest races east from the Ohio Valley. The
depth of the 0C+ wet bulb air will range from 4-5 kft thick
across the southwest (providing a deep layer for the snowflakes
to melt into supercooled droplets falling into sfc air in the
20s. A more borderline and shallower warm layer will be present
across the Central Mtns and Susq Valley where a bit of wet snow
followed by an extended period of sleet will occur Wednesday
night into the rush hour period of Thursday, before possibly
transitioning/ending as a few to several hour period of
-FZRA/-FZDZ.
Collaborated with surrounding WFOs and WPC to upgrade the Wint
Stm Watch to an ICE STORM WARNING across the Laurel Highlands
and immediately adjacent areas.
Liq Equivalent QPF amounts are generally 0.25-0.5" along and
north of I-80, >0.75" in the Laurels, and 0.5-0.75" east of I-99
and south of I-80. Accounting for the expected precipitation
type transitions and timing, the current forecast paints
snow/sleet accumulations of 1 to 2 inches over the majority of
central and northeast PA (with slightly higher amounts under
the aforementioned Wednesday snow band), and widespread 0.10"+
ice accretion with amounts >0.25" to perhaps 0.50 of an inch
favored in the Laurel Highlands through midday Thursday.
By Thursday morning, precipitation will either transition to
mainly rain or shut off during the morning hours as the ill
defined surface low races east of PA.
There is still some question with regard to how fast the
warmer/less dense air in on Thursday as the moisture gradually
lifts out to the northeast and llvl p-gradient weakens possibly
keeping the shallow colder air locked in the valleys of central
PA.
Some freezing rain/drizzle is likely to linger longest in
northeast PA as is typical with these systems.
Temperatures are progged to rebound considerably Thursday
afternoon across the far SW, but readings above to low 40s
appear less and less likely for much of the Central Mtns and
Susq Valley.
It is difficult to scour out the cold air after these events,
so trending below guidance seems prudent. Highs in the upper 30s
low 40s areawide should help to melt much of the ice during the
afternoon and evening before cooler air filters in from the
north as another cold front moves in.
&&
.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
By Thursday night, a digging upper trough in the wake of a cold
front should drop temperatures back toward normal. Gradient
winds could result in some gustiness Thursday night into Friday
between systems. Fortunately, the thaw Thursday afternoon should
limit any potential for power outages that could result from
the combination of gusty winds and ice- covered trees and power
lines. Skies trend brighter/less cloudy on Friday with no
precipitation expected.
The active period of weather will continue through and beyond
this extended period with wintry systems appearing likely every
2.5 to 3.5 days. Despite fairly flat and fast upper level flow,
another potentially significant winter weather event is possible
this weekend. The surface low with this system may track a bit
farther south compared to the Wednesday/Thursday storm, and if
it stays south of PA, more snow would be favored compared to the
icy/mix p-types for the midweek storm. Onset could be as early
as Saturday morning, though Saturday afternoon through Sunday
morning is most likely at this point.
WPC probabilities of liquid equivalent snow/sleet exceeding
0.25" are maximized north of I-76 (40-70%), supporting the idea
that snow would be favored farther north with a changeover to
sleet and/or plain rain farther south as the system moves
through. Changes in precipitation type, timing, and amount
forecasts are a guarantee, but those with travel plans this
coming weekend should continue to monitor the forecast.
&&
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
Late evening update.
Winds kicking up at some spots a bit stronger than I expected.
The main thing is very strong warm advection between 600 and
700 mb on about 50 knots of wind, has resulted in a rapid
advance of mid level clouds into western PA from the west and
northwest. The airmass below is quite dry, so expect little if
anything to reach the ground.
Adjusted the TAFS for these 2 factors mentioned here.
00Z TAFS sent.
Aside from BFD, looking at clear skies with VFR conditions
overnight, as high pressure builds overhead. A northwest wind
off the Great Lakes will keep lower CIGS and flurries across
BFD overnight. Conditions should improve Wednesday morning,
as winds shift to the southeast and the sun comes up.
Most of Wednesday should feature just some high and mid clds
later in the day. There could be a brief round of light snow,
but most guidance keeps the area dry through late afternoon.
Main issue Wednesday night into Thursday morning will be an
event like Sunday, some snow to start, the a mix of snow,
sleet, and freezing rain.
The precipitation should taper off by early afternoon if not
sooner on Thursday, and temperatures are expected to climb into
the 40s. This will end the threat of mixed precipitation.
Outlook...
Thu...Widespread rain, or freezing rain in the morning, ending
in the afternoon.
Fri...Dry weather.
Sat...A wintry mix. Impacts likely.
Sun...Still a chance of mixed precipitation early, then
improving conditions.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 10 PM Wednesday to noon EST
Thursday for PAZ004>006-010>012-018-019-026>028-036-037-041-
042-045-046-049>053-056>059-063>066.
Ice Storm Warning from 7 PM Wednesday to noon EST Thursday for
PAZ017-024-025-033>035.
&&
$$
SYNOPSIS...Lambert/Banghoff
NEAR TERM...Lambert/Dangelo
SHORT TERM...Lambert
LONG TERM...Dangelo/Banghoff
AVIATION...Martin
NWS CTP Office Area Forecast Discussion
